1. Field of the Invention
The present invention generally relates to hardcopy apparatus, such as copiers, printers, scanners, and facsimiles, and more particularly to improved media advancing devices for such apparatus.
2. Description of the Prior Art
In hardcopy apparatuses and particularly in apparatuses handling media of large size, such as large format printers, a printed medium is outputted from the printer by outputting devices that may damage the quality of the printout. Conventional outputting devices, in order to advance printed media, employ elements for holding the medium having direct contact with the printed surface. This may cause markings on the medium, ink smearing and other adverse affects on the print appearance.
As an example, the prior art has employed pinch wheels on top of the overdrive roller for outputting printed media. These devices may damage the printout with pinch wheel marks and further require the need to employ a mechanism or a structure to hold the pinch wheels.
To overcome the problem of adverse affects on the print appearance, U.S. Pat. No. 6,786,664 discloses a device for advancing a medium on a platen including a combination of an overdrive roller with a negative pressure mechanism, a shim being provided in the gap between the platen and the overdrive roller. Thus, the shim allows controlling the entrance for air through the gap between the platen and the overdrive roller. However, the presence of the shim on the platen creates a mechanical discontinuity which may impact negatively on the smooth displacement on the medium and could cause dirt accumulation. In any case, the shim can only prevent entrance of air in the gap if it comes directly in contact with the roller, leading to creating friction when the roller rotates.
The present invention provides an improved media advancing device and an improved method of displacing a medium.